Ring-Opening Polymerisation of rac-Lactide Using a Calix[4]arene-Based Titanium (IV) Complex

cone-25,27-Dipropyloxy-26,28-dioxo-calix[4]arene titanium (IV) dichloride(1)has been assessed in the ring-opening polymerisation ofrac-lactide (L,D-LA). The polymers formed (PLDA) turned out to display an isotactic stereoblock microstructure (determined by NMR) despite the fact that the catalyst hasC2vsymmetry. Two techniques were applied for initiating the polymerisation reaction, microwave irradiation, and conventional thermal treatment. The polymers obtained were all characterised by NMR, IR, HPLC-SEC, DSC, and MALDI-TOF analysis. The use of microwave irradiation, applied for the first time to calixarene-based catalysts in the presence of therac-lactide monomer, increased the polymerisation rate compared with that obtained by the other method. On the other hand, standard thermal treatment enabled a slightly better control than microwave irradiation over the molecular weight and molecular weight distribution of the polylactides formed

Ring-Opening Polymerisation of rac

cone-25,27-Dipropyloxy-26,28-dioxo-calix[4]arene titanium (IV) dichloride (1) has been assessed in the ring-opening polymerisation of rac-lactide (L,D-LA). The polymers formed (PLDA) turned out to display an isotactic stereoblock microstructure (determined by NMR) despite the fact that the catalyst has C2v symmetry. Two techniques were applied for initiating the polymerisation reaction, microwave irradiation, and conventional thermal treatment. The polymers obtained were all characterised by NMR, IR, HPLC-SEC, DSC, and MALDI-TOF analysis. The use of microwave irradiation, applied for the first time to calixarene-based catalysts in the presence of the rac-lactide monomer, increased the polymerisation rate compared with that obtained by the other method. On the other hand, standard thermal treatment enabled a slightly better control than microwave irradiation over the molecular weight and molecular weight distribution of the polylactides formed

Water spectral pattern as a marker for studying apple sensory texture

Aquaphotomics is a scientific discipline which investigates the water-light interactions in biological systems by using NIR spectroscopy and multivariate analysis to relate water absorption patterns to bio-functionalities. This work aimed at evaluating the feasibility of Aquaphotomics to study apple fruit sensory texture. ‘Braeburn’, ‘Gala’ and ‘Kanzi®’ apples were analyzed by a MicroNIR spectrometer and for mechanical, structural and texture sensory characteristics. Cluster analysis on sensory texture attributes showed four different profiles for each cultivar having different water spectral patterns (WASP). On average, the WASP of mealy apples showed the highest absorbance values at 1364, 1372 and 1382 nm and the lowest in the 1438-1492 nm range suggesting a preponderance of water structures with weak-hydrogen bonds; the opposite was found in crispy and juicy apples indicating the presence of more organized water structures with medium-strong hydrogen bonds. This WASP difference could be due to a different softening rate: apples clustered as firm/crispy/juicy had the highest firmness and the lowest intercellular spaces, while mealy apples had low firmness and high intercellular spaces indicating a more advanced softening. The chemical changes due to the pectin hydrolyzation could affect the water structures. The Aquaphotomics approach could be a useful tool for studying the sensory texture of fruits as water structures actually change in apples with different textural characteristics whatever the cultivars

L-Lactide polymerization by calix[4]arene-titanium (IV) complex using conventional heating and microwave irradiation

AbstractSince the first contributions by Gedye and Giguere in 1986, growing attention has been registered on the use of microwave heating in organic synthesis. However still many aspects need to be clarified especially about the so called "microwave effect" and the possible degradation phenomena that may be recognized during polymer synthesis. In this work the complex cone-25,27- dipropyloxy-26,28-dioxo-calix[4]arene titanium (IV) dichloride (1) has been tested for the ring opening polymerization of L-lactide, comparing the effect of conventional heating with a possible microwave assisted strategy. The polymers obtained were fully characterized (NMR, IR, HPLC-SEC, DSC, MALDI-TOF and WAXD analysis). As expected the use of microwave irradiation induced an increase of the polymerization rate. On the other side the use of microwaves resulted in a slight loss of the control over molecular weight and molecular weight distribution if compared with a conventional thermal treatment

L-Lactide polymerization by calix[4]arene-titanium (IV) complex using conventional heating and microwave irradiation

AbstractSince the first contributions by Gedye and Giguere in 1986, growing attention has been registered on the use of microwave heating in organic synthesis. However still many aspects need to be clarified especially about the so called "microwave effect" and the possible degradation phenomena that may be recognized during polymer synthesis. In this work the complex cone-25,27- dipropyloxy-26,28-dioxo-calix[4]arene titanium (IV) dichloride (1) has been tested for the ring opening polymerization of L-lactide, comparing the effect of conventional heating with a possible microwave assisted strategy. The polymers obtained were fully characterized (NMR, IR, HPLC-SEC, DSC, MALDI-TOF and WAXD analysis). As expected the use of microwave irradiation induced an increase of the polymerization rate. On the other side the use of microwaves resulted in a slight loss of the control over molecular weight and molecular weight distribution if compared with a conventional thermal treatment

Temporal XML

Temporal XML is a timestamped instance of an XML data model or, alternatively, an XML document with specially interpreted timestamps which is parsed into a timestamped instance of an XML data model. An XML data model instance is a tree or graph in which each node corresponds to an element, attribute, or value, and each edge represents the lexical nesting of the child in the parent\u2019s content. In temporal XML, a timestamp is added to some nodes or edges in the instance. The timestamp represents the lifetime of the node or edge in one or more temporal dimensions, usually valid time or transaction time

Time- and spatially-resolved spectroscopy to determine the bulk optical properties of 'Braeburn' apples after ripening in shelf life

Bulk optical properties, in terms of absorption (μa) and reduced scattering coefficients (μ′s), can be used for the non-destructive monitoring of fruit quality during ripening. In this study, the performance of time-resolved (TRS) and spatially-resolved (SRS) spectroscopy were compared by analyzing ‘Braeburn’ apples over a 21 d period of ripening. Nine batches of 20 apples each were measured on the blush side by TRS (540−1064 nm) and SRS (550−1000 nm). Every fruit was analyzed for skin color, texture characteristics, relative internal space volume (RISV), total solid soluble and titratable acidity contents. TRS absorption spectra showed two maxima, the highest at 980 nm (water) and the second at 670 nm (chlorophyll), while in SRS spectra the main peak was measured at 550 nm (anthocyanins) followed by that at 670 nm. The values of μa580SRS and of μa670SRS were much higher than those measured at the same wavelengths by TRS suggesting that TRS and SRS actually explore the apple tissue (skin and/or flesh) in a different way. The values of μa980TRS were higher than those of μa980SRS, probably due to the fact that water content was lower in the skin (mostly probed by SRS) than in the flesh (mostly probed by TRS). No significant correlations were found between μa580SRS and μa580TRS and between μa980SRS and μa980TRS but a low positive relationship was observed between μa670TRS and μa670SRS. On the contrary, high correlations were found between μa670SRS and the spectral index IAD (index of absorbance difference) related to chlorophyll in the skin and between μa580SRS and the spectral index ARI (anthocyanin reflectance index), related to anthocyanin content in the peel, suggesting that μa580SRS is linked to the development of the red color in the peel. Both μa670TRS and μa670SRS decreased during fruit ripening, indicating a decline in chlorophyll in the flesh and skin, respectively. During the shelf life period, apples became soft and mealy, as mechanical and acoustic parameters decreased and RISV increased. Fruit softening was accompanied by increasing values of both μ′sTRS and μ′sSRS. The μ′sTRS and μ′sSRS were positively related to each other, were positively correlated to RISV and negatively related to mechanical and acoustic parameters. Both the TRS and SRS technique were able to follow ripening processes in ‘Braeburn’ apples during the shelf life period, as absorption phenomena were related to changes in pigments present in the fruit flesh and skin, while scattering events mirrored changes in the flesh texture.status: publishe